Figure 1.

Measurements of linear, angular, and pharyngeal airway dimensions. HRP, horizontal reference plane; VRP, vertical reference plane; S, Sella; N, Nasion; Ba, Basion; PNS, posterior nasal spine; A, A point; B, B point; D1, the length at which the PNS-Ba line intersects the pharyngeal airway; D2, the narrowest distance between the soft palate and the posterior pharyngeal wall; D3, the narrowest distance between the base of tongue and the posterior pharyngeal wall; Area, the area between D1 and D3.

Mx base and Mn base indicate A point and B point perpendicular distances to VRP, respectively. Mn plane indicates Gonion-Menton line.